LEAD AND ZINC DISTRIBUTION IN BRASSICA JUNCEA AND ARID SOIL AMENDED WITH MINE TAILINGS AND BOKASHI

Indian mustard (Brassica juncea) was grown in soil amended with mine tailings, bokashi and EDTA (ethylen-diaminetetraacetic acid), alone or mixed, for six weeks. Plant roots and shoots were then collected and analysed for Pb, Zn, Cd, Cu, Fe, Hg, As and Sb. Additionally, the soil treatments were analysed for Pb and Zn fractionation, exchangeable cations and microbial activities after harvesting the plants. The accumulation of all metals in roots was higher than in shoots. The soil treatment amended with bokashi had a high concentration of Na and Mg. The addition of mine tailings alone to soil inhibited 80% of the CO2 production, 18% of the dehydrogenase activity, and 7% of the N-mineralization. The addition of bokashi reduced the inhibition, but the addition of EDTA increased the inhibition of CO2 and stimulated the dehydrogenase activity and N-mineralization. Factor analysis supported the association of Na with the accumulation of heavy metals in the roots, and potential available Pb and Zn in fractions II, III, IV and IV. CEC (cation exchange capacity) was associated with heavy metals in shoots as well as soluble and interchangeable Pb and Zn. Brassica juncea was tolerant to poly-metals and high Na concentrations, and allowed low translocation to the shoots.